An antenna is a necessary component in a communication system. The performance of the antenna is directly related to quality of receiving and transmission of signals. Particularly, the difficulty in design of antennas in a communication equipment terminal is increased day by day. With network pavement and application of Long Term Evolution (LTE), the antenna needs to cover a wider frequency band, and a larger space is required. However, at present various communication terminals, in particular mobile phone terminals, have been developed in lightening and thinning, minimizing and globalizing ways, and their aesthetic properties shall be considered meanwhile. Therefore, it is impossible to leave a large enough space for the antenna. A limited space would always directly result in insufficient bandwidth, and this is the biggest problem in the design of the antenna. To solve this problem, generally, a conventional method for expanding the bandwidth of the antenna is to increase parasitic units coupled with a main radiator to generate harmonic with a required frequency band. But this method will result in loss of bandwidth of part of the frequency band.